JPH0619207A - Charge control agent and electrophotographic toner containing same - Google Patents

Abstract

PURPOSE:To provide a charge control agent free from heavy metals and excellent in charge rising characteristic, charge amt., aging stability and dispersibility when a toner is prepared by forming the agent with a specified compd. having a specified grain size. CONSTITUTION:This charge control agent consists of a compd. having <=5mum grain diameter and shown by the formula where X is -SO2- or -C(CH3)2. The compd. is dissolved in an alkaline soln., and the crystal is then deposited by acid. Consequently, the compatibility with a resin is improved, the photographic toner contg. the agent has high specific charge amt. and good aging stability, and a high-definition picture is stably formed in electrostatic recording even after the toner is preserved for a long time. Besides, since the agent is colorless and has a positive or negative charging performance, a black toner and a color toner are produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner used for developing an electrostatic latent image in electrophotography, electrostatic recording and the like, and a charge control agent used therefor.

[0002]

2. Description of the Related Art Colored fine particles generally called toner are
The binder resin is mainly composed of a colorant, a charge control agent, etc. Among them, the charge control agent having a function of retaining the charge by frictional charging with the carrier and controlling the charge characteristic of the toner is particularly important among the toner components. It is an ingredient. It is possible to retain the charge by friction with the carrier even with a toner produced only with a colorant and a binder resin without using a charge control agent, but since the chargeability is poor, a fogging phenomenon occurs and You can only get inferior images. In addition to the charging property, the quality characteristics required of the toner are required to be excellent in stability over time, fluidity, fixability, etc., but these are all greatly influenced by the charge control agent used. is there.

As charge control agents conventionally added to toners, 1) 2: 1 type metal-containing complex salt dyes as colored negative charge control agents (eg, JP-B-45-26478, JP-B-41-2).
0153) Phthalocyanine pigment (eg, JP-A-52-45)
931) Further, as an example of a colorless negative charge control agent, a metal complex of an aromatic dicarboxylic acid (eg, JP-B-59-7384)
Metal complexes of salicylic acid (eg, JP-A-57-10494)
0) or the charge control agents described in JP-A-61-1349, etc.

2) As positive charge control agents, nigrosine dyes, triphenylmethane dyes, various quaternary ammonium salts (Journal of the Electrostatic Society, 1980, Vol. 4, No. 3, P-144),
Organotin compounds such as dibutyltin oxide (eg, Japanese Patent Publication No. 57-29704) are known. Toners containing them as charge control agents are required to have good quality characteristics such as chargeability and stability over time. Does not fully satisfy.

For example, 2: 1 known as a negative charge control agent
Although the toner containing the metal-containing complex salt dye has a tentative level of high charge amount, the 2: 1 type metal-containing complex salt dye generally has a drawback that the dispersibility in the binder resin is poor. Therefore, the toner is not evenly distributed in the binder resin, the charge amount distribution of the obtained toner is extremely lacking in sharpness, and the obtained image has low gradation and poor image forming ability.

Further, the 2: 1 type metal-containing complex salt dye has a drawback that it can be used only for toner having a limited hue centered on black, and when used as a color toner, the sharpness of the colorant is impaired. I will end up.

An example of a negatively charged negative charge control agent is a metal complex of an aromatic dicarboxylic acid (Japanese Examined Patent Publication 59).
-7384) This product has a drawback that it cannot be completely colorless and has a difficulty in its dispersibility. Further, as a colorless negative charge control agent having relatively good charging performance, a metal complex of salicylic acid can be mentioned (JP-A-57-1049).
40) This substance contains heavy metals, and its safety is problematic. As a negative charge control agent which is colorless and does not contain heavy metals, JP-A-61-1349 and JP-A-63-38958 are disclosed.
However, since the melting point of this compound is lower than the processing temperature (180 ° C. to 260 ° C.) at the time of toner production, various problems are caused during toner processing, and stable toners are produced. The disadvantage that it is difficult to put out,
There is a drawback that the rising speed of charging is slow. Also,
Nigrosine dyes and triphenylmethane dyes, which are known as positive charge control agents, are colored by themselves,
It has a drawback that it can be used only for a toner having a limited hue centered on black, and that the stability of the toner over time in continuous copying is not good. Further, the conventional quaternary ammonium salt has a drawback that it is inferior in stability over time due to insufficient moisture resistance when made into a toner, and does not give a good quality image upon repeated use.

Japanese Patent Publication No. 4-16109 describes that a bisphenol compound works as a good charge control agent in a toner. However, these compounds have a large particle size of 10-15 microns and are not sufficiently effective as a charge control agent.

[0009]

A charge control agent which is colorless and is positively or negatively charged, has excellent charge rise characteristics, charge amount and stability over time, and is excellent in dispersibility during toner production.
Another object is to provide a charge control agent that does not contain heavy metals.

[0010]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that a specific compound having a specific particle size achieves the above-mentioned object. Completed That is, the present invention provides: (1) Formula (1) having a particle size of 5 μm or less

[0011]

[Chemical 1]

[0012] (In the formula (1), X is -SO ₂ - or -C (CH _{3) 2} - a representative) charge control agent comprising a compound represented by the formula (2) wherein according to the above (1) ( The compound of 1) is dissolved in an alkaline solution, and crystals are then precipitated with an acid. (3) The method of producing a charge control agent as described in (1) above, wherein the charge control agent as described in (1) above is used. An electrophotographic toner containing the same is provided.

The charge control agent of the present invention has good compatibility with a binder resin, and the electrophotographic toner of the present invention containing the charge control agent has a high specific charge amount and good stability over time. Therefore, even when stored for a long time, a stable and clear image is provided in the image formation of electrostatic recording. Since the charge control agent of the present invention is colorless and has positive or negative charging performance, black toner and color toner can be produced. In addition, since this product does not contain heavy metals, it is highly safe for the environment. In addition, when the toner is prepared by the suspension polymerization method or the emulsion polymerization method, the heavy metal does not inhibit the polymerization as seen in the metal-containing charge control agent, so that the toner can be stably produced. .

The present invention will be described in detail. The compound of the formula (1) is, for example, 4,4′-dihydroxydiphenylsulfone or 4,4′-dihydroxydiphenyl-2,2-
It is obtained by brominating propane with bromine, hydrobromic acid, etc., and made into fine particles by the following method. That is, the compound of formula (1) is added to an alkaline aqueous solution and stirred to completely dissolve it. Crystals are precipitated by pouring an acidic aqueous solution into the thus obtained aqueous solution for neutralization, or by pouring the aqueous solution into the acidic aqueous solution to obtain a fine particle of the compound of the formula (1). The temperature at which the compound of formula (1) is dissolved in the alkaline solution and the temperature at which crystals are precipitated by acid are 0 ° C-9.
The temperature is 0 ° C., preferably 15 ° C.-30 ° C. The alkali agent used may be an alkali metal compound or an alkaline earth compound, but is preferably caustic soda, sodium carbonate,
Caustic potassium and potassium carbonate are used. The amount of the alkaline agent used is 1 to 3 times the molar ratio with respect to the compound of the formula (1), and the concentration of the alkaline aqueous solution is usually 5 to 30% by weight. Acids such as mineral acids and organic acids can be used for neutralization (crystal precipitation), but sulfuric acid, hydrochloric acid, acetic acid and the like are preferably used. The amount of the acid used is such that the pH of the alkaline aqueous solution containing the compound of formula (1) is 2 to 6, preferably 4 to 6, and the concentration of the acid used is 3 to 95% by weight.
It is preferably 5 to 20% by weight. The crystal obtained by the above operation has a particle size of 5 μm or less, preferably 1-3.
The microparticles are uniform particles having a size of μm, and the toner for electrophotography of the present invention is prepared by using the particles as a charge control agent.

As a method for producing the electrophotographic toner of the present invention from the finely divided compound of the formula (1), a mixture of the finely divided compound of the formula (1), a colorant and a binder resin is heated in a kneader. , A method of kneading the binder resin in a molten state by a device capable of heating and mixing such as two rolls, and then cooling and solidifying the mixture to a particle size of 3 to 20 μ by a crusher such as a jet mill or a ball mill. The colorant, the binder resin, and the compound of formula (1) are dissolved in a solvent (eg, acetone, ethyl acetate), stirred, and then poured into water for reprecipitation, filtered, dried, and then pulverized with a pulverizer such as a ball mill. -A method obtained by pulverizing to a particle size of 20μ, the compound of formula (1), the colorant and the monomer of the binder resin are uniformly suspended in water and stirred. A method in which a monomer is polymerized in the form of fine particles to form a precipitate, and the precipitate is filtered, washed with water and dried to form a fine particle powder, which is then classified to obtain an electrophotographic toner having a particle size of 3 to 20 μ, etc. There is. Further, the outer shell of a microcapsule toner having a form in which a soft particle upper core material (core particle) containing a low melting point resin for pressure fixing, a coloring component, a magnetic material, etc. is covered with a hard outer shell having a protective function and a charge control function. It can also be used as a material. Further, colored fine particles containing no charge control agent are prepared by the above-mentioned method, and then the compound of the formula (1) alone or together with an external additive such as colloidal silica is fixed and added to the particle surface by a mechanochemical method or the like. You can also do it.

In these cases, the binder resin component is usually 9
9 to 65%, more preferably 98 to 85%, and the colorant is 1.
0 to 15%, more preferably 1.5 to 10%, the charge control agent of the present invention is 0.1 to 30%, more preferably 0.5 to 5%.
Are used in the ratio (both are weight ratios). Further, a charge control agent other than the charge control agent of the present invention can be used in combination.

Examples of colorants that can be used in the electrophotographic toner containing the charge control agent of the present invention include carbon black and
Ultramarine, iron black, activated carbon, copper oxide, manganese dioxide, yellow lead,
Zinc yellow, cadmium yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, red yellow lead,
Inorganic pigments such as molybdenum orange, red iron oxide, cadmium red, manganese purple, titanium oxide, zinc sulfide, chromium green, chromium oxide and antimony white, CI. Pigment Yellow 1, CI. Pigment Red 9, CI. Pigment Blue 15, Aniline Black, Naphthol Yellow S, Benzidine Yellow GR, Quinoline Yellow Lake, Anthrapyrimidine Yellow, Hansa Yellow G, Permanent Yellow NCG, Pyrazolone Orange, Indanthrene Brilliant Orange GK, Pyrazolone Red, Brilliant Carmine 6B, Rhodamine Lake B. , Quinacridone, alizarin lake, thioindigo red, thioindigo maroon, brilliant carmine 3B, methyl violet lake, dioxazine violet, aniline blue, metal-free phthalocyanine blue, phthalocyanine blue, fast sky blue, indanthrene blue BC, phthalocyanine green, Organic pigments such as malachite green lake and final yellow green G,
CI. Solvent Yellow 93, CI. Solven Yored 146, CI. Solvent Blue 35, CI. This Spurs Yellow 42, CI. This Spurs Red 59, C
I. Disperse Blue 81, CI. Solvent Red 4
9, CI. Solvent Red 52, CI. Solvent Red 109, CI. Basic Red 12, CI. Basic Red 1, CI. Direct Red 1, CI. Acid Red 1, CI. Basic Red 1, CI. Direct Red 4, CI. Mordant Red 30, C
I. Direct Blue 2, CI. Acid Blue 9, C
I. Basic Blue 3, CI. Basic Blue 5,
CI. Acid Blue 15, CI. Mordant Blue 7, CI. (CI is an abbreviation for color index, the same applies hereinafter) and other conventionally known colorants such as oil-soluble dyes can be mentioned.

As the binder resin, polystyrene, styrene-methacrylic acid copolymer, styrene-methacrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-acrylic acid ester copolymer, styrene-acrylonitrile copolymer are used. Polymers, acrylic resins, styrene-maleic acid copolymers, polyvinyl chloride, polyvinyl acetate, olefin resins, polyester resins, polyurethane resins, epoxy resins and the like can be used alone or in combination. Further, as the monomer of the binder resin, the monomer of the above resin is used, and specifically, styrene, α-
Vinyl aromatic hydrocarbon monomers such as methylstyrene, vinyltoluene, chlorostyrene, ethylstyrene, and divinylbenzene, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, Monomers of acrylic compounds such as octyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, phenyl methacrylate, acrylonitrile, methacrylonitrile, Monocarboxylic acids having a double bond such as acrylamide, maleic acid, methyl maleate,
Dicarboxylic acids such as butyl maleate, dimethyl maleate, phthalic acid, succinic acid, and terephthalic acid, ethylene, propylene, butylene, vinyl methyl ketone, vinyl hexyl ketone, vinyl methyl ether, vinyl isobutyl ether, and other vinyl monomers, Ethylene glycol, diethylene glycol, triethylene glycol,
1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,4-hexanediol, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and other polyol compounds, p-phenylene diisocyanate, Isocyanates such as p-xylylene diisocyanate, 1,4-tetramethylene diisocyanate, ethylamine,
Butylamine, ethylenediamine, 1,4-diaminobenzene, 1,4-diaminobutane, monoethanolamine, and other amines, diglycidyl ether, ethylene glycol diglycidyl ether, bisphenol A glycidyl ether, hydroquinone diglycidyl ether, and other epoxy compounds, etc. Alternatively, they can be mixed and used.

Further, in the electrophotographic toner containing the charge control agent of the present invention, a fluidizing agent such as silicon oxide, an antifoggant such as mineral oil, various magnetic substances for one-component system, and conductivity imparting such as zinc oxide. Agents and the like may be added if necessary. The toner obtained in the present invention is mixed with iron powder (carrier) of about 200 mesh at a weight ratio of 3-8: 97-92 (toner: iron powder) to form a developer.
It is used in the developing process in electrophotography.

The electrophotographic toner containing the charge control agent of the present invention has a sharp charge amount distribution and good stability over time as compared with the toner using the conventional charge control agent. As a result, an image with extremely high gradation is obtained, and the repetitive image forming ability is extremely good.

[0021]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, “parts” means “parts by weight” unless otherwise specified.

Example 1 To 200 parts of water, 9.6 parts of caustic soda was added to prepare an alkaline aqueous solution. 4,4'-dihydroxy-3,
5,3 ′, 5′-tetrabromodiphenyl sulfone 50
Parts (particle diameter: 10-15 μm) are added and completely dissolved. While maintaining the temperature at 20 ° C. to 30 ° C., an acidic aqueous solution prepared by diluting 15 parts of concentrated sulfuric acid with 200 parts of water is dropped into the complete solution over 30 minutes to 1 hour with stirring. After finishing the dropwise addition of the acidic aqueous solution, stirring for 30 minutes and confirming that it is weakly acidic,
Precipitated crystals were filtered off, washed with 300 parts of water and dried to form fine particles of 4,4′-dihydroxy-3,5.
49.5 parts of the charge control agent of the present invention consisting of 3 ', 5'-tetrabromodiphenyl sulfone was obtained. It was confirmed by an electron microscope that the particles were fine particles having a particle size in the range of 1-3 μm. The X-ray diffraction diagram of this product is shown in Fig. 2.
It is (Mp = 290-291 ° C.) Incidentally, the X-ray diffraction diagram is based on the powder X-ray diffraction method, and Cu-Kα
The diffraction state by the line is recorded by using a proportional counter.

Example 2 The procedure of Example 1 was carried out in the reverse order, that is, 4,4'-dihydroxy-3,5,3 ', 5' in a sulfuric acid aqueous solution.
-A caustic aqueous solution of tetrabromodiphenyl sulfone was added dropwise to precipitate crystals. As a result of electron microscope observation, the crystals thus obtained were also in the range of 1-3 μm in particle size, as in Example 1.

Examples 3 and 4 Crystals were deposited in the same manner as in Example 1 except that the type of acid was changed to hydrochloric acid (Example 3) and acetic acid (Example 4) instead of sulfuric acid. Let The crystals thus obtained by electron microscope observation were also fine particles having a particle size in the range of 1-3 μm, as in Example 1.

Example 5 To 250 parts of water, 17.2 parts of sodium carbonate was added to prepare an alkaline aqueous solution. 4,4'-dihydroxy-
45 parts of 3,5,3 ′, 5′-tetrabromodiphenyl sulfone are added to complete the solution. While maintaining the temperature at 20 ° C. to 30 ° C., 10 parts of concentrated sulfuric acid was added to 1 part of water with stirring in the complete solution.
The acidic aqueous solution diluted to 00 parts is added dropwise over 30 minutes to 1 hour. After the addition of the acidic aqueous solution was completed, the mixture was stirred for 30 minutes to confirm that it was weakly acidic, and then the precipitated crystals were filtered off.
4,4 'finely divided by washing with 300 parts of water and drying
-Charge control agent 49.3 of the invention consisting of -dihydroxy-3,5,3 ', 5'-tetrabromodiphenyl sulfone
I got a part. It was confirmed by electron microscope observation that the particles were fine particles having a particle size in the range of 2-4 μm.

Example 6 Crystals were deposited in the same manner as in Example 5 except that the kind of alkali was changed to caustic potash instead of sodium carbonate. Similarly, the crystals obtained in this way
It was confirmed by electron microscope observation that the particles were particles having a particle diameter in the range of 1-3 μm.

Example 7 To 250 parts of water, 6.4 parts of caustic soda was added to prepare an alkaline aqueous solution. 4,4'-dihydroxy-3,
Completely dissolve by adding 42.0 parts of 5,3 ′, 5′-tetrabromodiphenyl-2,2-propane. Temperature is 20 ℃ -3
1% concentrated sulfuric acid was added to the complete solution while stirring at 0 ° C. with stirring.
An acidic aqueous solution prepared by diluting 0 part with 100 parts of water for 30 minutes to 1
Drop over time. After dropping the acidic aqueous solution, 30
After the mixture was stirred for minutes and confirmed to be weakly acidic, the precipitated crystals were separated by filtration, washed with 300 parts of water and dried to give fine particles of 4,4′-dihydroxy-3,5,3 ′, 41.5 parts of the charge control agent of the present invention consisting of 5'-tetrabromodiphenyl-2,2-propane was obtained. It was confirmed by electron microscope observation that the particles were fine particles having a particle size in the range of 2-4 μm.

Example 8 Styrene-butyl acrylate copolymer (binder) 100 parts Low molecular weight polyethylene 3 parts CI. Disperse Yellow 164 (colorant) 1.2 parts Charge control agent obtained in Example 1.5 1.5 parts After melt-mixing treatment (10 minutes) with a kneader adjusted to 130-140 ° C., the mixture having the above composition It was cooled and solidified. Then, after coarsely pulverizing with a coarse pulverizer, fine pulverization with a jet mill pulverizer and further classification with an airflow classifier to obtain an electrophotographic toner of the present invention having a particle size of 5 to 20 μm. In addition, when the dispersibility of the charge control agent during the melt-mixing treatment is judged by observing with a microscope, the particles before atomization (particle size 10-15 microns) have a large particle size and therefore particles are not crushed and dispersed. It was confirmed that the dispersibility was extremely good in the case of Example 1 after the formation of fine particles, whereas the dispersibility was poor.

The toner thus obtained was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer A. Next, the initial specific charge amount of the developer A was measured by a blow-off charge amount measuring device and found to be -18.2 μC / g.

Further, when copying was carried out by a copying machine using this developer A, a clear yellow image excellent in gradation and not hindering the original hue of the colorant was obtained. Further, when a temporal stability test (charge amount temporal stability test, charge amount moisture resistance stability test) was performed using the developer A, the results shown in Table 1 below were obtained.

Table 1 Charge amount aging stability test (unit, −μC / g) Time (h) 0.25 0.5 1 2 4 6 Developer A 15.7 16.6 18.1 18.4 19. 9 20.1 Charge amount humidity resistance stability test (unit, -μC / g) Initial charge amount Charge amount after humidity resistance test Decay rate (%) 18.2 18.0 1.1

As shown in the above results, the temporal stability of the developer A was extremely excellent.

The stability test with time was performed according to the following method. Charge amount temporal stability test A developer (mixture of toner and iron powder carrier) is weighed in a poly container and contact charged by a ball mill at 120 rpm for 6 hours, and the charge amount of the toner at each time is blow-off method. To measure. Charge amount moisture resistance stability test Similar to the charge amount aging stability test, the developer was weighed in a poly container, the container was opened and left at 35 ° C and 90% RH for 2 days, and then the ball mill was rotated at 120 rpm. After contact charging for 15 minutes, the charge amount of the toner is measured by the blow-off method.

Example 9 Styrene-butyl acrylate copolymer (binder) 100 parts Low molecular weight polyethylene 3 parts CI. Disperse Yellow 164 (colorant) 1.2 parts Charge control agent obtained in Example 1.5 1.5 parts After melt-mixing the mixture of the above composition with a kneader adjusted to 130-140 ° C. (10 minutes) It was cooled and solidified. Then, after coarsely pulverizing with a coarse pulverizer, fine pulverization with a jet mill pulverizer and further classification with an airflow classifier to obtain an electrophotographic toner of the present invention having a particle size of 5 to 20 μm. When the dispersibility during the melt mixing treatment was observed with a microscope in the same manner as in Example 8, the dispersibility was extremely good.

The toner thus obtained was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer B. Next, the initial specific charge amount of this developer B was measured by a blow-off charge amount measuring device and found to be +15.6 μC / g.

Further, copying was carried out by a copying machine using this developer B, and a clear yellow image excellent in gradation and not hindering the original hue of the colorant was obtained. Further, when a time-dependent stability test (charge amount time-dependent stability test, charge amount humidity resistance stability test) was performed using the developer B, the results shown in Table 2 below were obtained.

Table 2 Charge amount temporal stability test (unit, + μC / g) Time (h) 0.25 0.5 1 2 4 6 Developer B 16.0 16.5 17.0 16.1 16.8 16.6 Charge amount Moisture resistance stability test (unit, + μC / g) Initial charge amount Charge amount after humidity resistance test Attenuation rate (%) 16.0 15.9 0.6

As shown in the above results, the temporal stability of the developer B was extremely excellent.

Example 10 Polyester resin 100 parts Carbon black (coloring agent) 6.0 parts Charge control agent obtained in Example 1 1.5 parts

The mixture having the above composition was melt-mixed with a kneader adjusted to 150 to 180 ° C. (10 minutes), and then,
It was cooled and solidified. Then after coarse crushing with a coarse crusher,
The toner was finely pulverized with a jet mill pulverizer and further classified with an airflow classifier to obtain an electrophotographic toner of the present invention having a particle size of 5-20 μm. When the dispersibility during the melt mixing treatment was observed with a microscope in the same manner as in Example 8, the dispersibility was extremely good. The obtained toner was mixed with an iron powder carrier of about 200 mesh at a weight ratio of 3:97 (toner: iron powder carrier) to obtain a developer C. Next, when the initial specific charge amount of the developer C was measured by a blow-off charge amount measuring device, it was −20.6 μC / g. Further, this developer C
When a copy machine was used to make a copy, a black image excellent in gradation was obtained. Further, when a temporal stability test was conducted in the same manner as in Example 1 using the developer C, the results shown in Table 3 below were obtained.

Table 3 Charge amount temporal stability test (unit, -μC / g) Time (h) 0.25 0.5 1 2 4 6 Developer C 19.1 19.9 20.8 21.2 21. 5 21.4 Charge amount humidity resistance stability test (unit, -μC / g) Initial charge amount Charge amount after humidity resistance test Attenuation rate (%) 20.6 20.2 1.9

As can be seen from the above results, the stability of developer C with time and the stability against humidity were extremely excellent.

Example 11 Methyl styrene monomer 75 parts Ethyl acrylate monomer 20 parts Kayase Blue 814 (colorant) 1.8 parts Benzoyl peroxide 6 parts Charge control agent obtained in Example 7 2 parts A mixture of the above composition Using a homomixer, stir and mix for 5 minutes to form a homogeneous liquid substance, add this to a dispersion of water: 120 parts / magnesium carbonate: 2.3 parts, and stir for 5 minutes at 6500 rpm with a homomixer to obtain a uniform suspension. To get
Add this suspension to a 300 ml three-necked flask and
Polymerize at 70 ° C for 5 hours with stirring at rpm,
After cooling to 40 ° C., 90 parts of a 5% dilute hydrochloric acid aqueous solution was added, filtered, washed with water and dried at 40 ° C. to obtain an electrophotographic toner of the present invention having a particle size of 5 to 20 μm.

0.3 part of colloidal silica was mixed with 100 parts of the obtained toner by a Henschel mixer. This was mixed with about 200 mesh iron powder carrier and 3:97.
(Toner: iron powder carrier) mixed in a weight ratio of developer D
Got Then, the initial specific charge amount of this developer D was measured by a blow-off charge amount measuring device to be +16.2 μC.
/ G. Further, when copying was performed by a copying machine using this developer D, a clear red image excellent in gradation and not hindering the original hue of the colorant was obtained.
Further, a time-dependent stability test was conducted in the same manner as in Example 1 using Developer D, and the results shown in Table 4 below were obtained.

Table 4 Charge amount aging stability test (unit, + μC / g) Time (h) 0.25 0.5 1 2 4 6 Developer D 15.9 16.4 17.6 17.7 18.2 18.1 Charge amount Moisture resistance stability test (unit, + μC / g) Initial charge amount Charge amount after humidity resistance test Attenuation rate (%) 16.2 16.0 1.3

As shown in the above results, the temporal stability of the developer D was extremely excellent.

The charge control agent of the present invention has a particle size of 5 μm.
Since it is below, the dispersibility at the time of toner production is good, and it has the feature of improving the charging performance.The toner for electrophotography obtained from this has a sharper charging than the toner using a conventional charge control agent. It has a quantity distribution, moisture resistance and stability over time. As a result, an image with extremely high gradation is obtained,
And the repetitive image forming ability is very good. In addition, since the charge control agent itself is essentially colorless, it is possible to select an arbitrary colorant in accordance with the hue required for the color toner, and what is the original hue of the dye or pigment. It is also characterized by not inhibiting. Further, the charge control agent of the present invention containing no metal is also characterized by high safety to the environment.

[Brief description of drawings]

FIG. 1 is an X-ray diffraction diagram of the compound used in Example 1 before atomization, and FIG. 2 is an X-ray diffraction diagram after atomization. In the drawing, the horizontal axis represents the diffraction angle (2θ) and the vertical axis represents the diffraction intensity.

Claims (3)

[Claims] 1. A formula (1) having a particle size of 5 μm or less (In the formula (1), X is —SO ₂ — or —C (CH
₃ ) A charge control agent comprising a compound represented by ₂ ) 2. The method for producing a charge control agent according to claim 1, wherein the compound of formula (1) according to claim 1 is dissolved in an alkaline solution, and then crystals are precipitated with an acid. 3. An electrophotographic toner containing the charge control agent according to claim 1.